Assembly for prevention of backflow in valves

ABSTRACT

A valve assembly which is suitable for backflow prevention in a stop cock having an inlet, a seat and an outlet. The valve assembly may be attachable to the stop cock and includes a valve body having at least one opening and also including a valve chamber and a valve seat. There is provided a balance tube in the valve body which communicates with the valve chamber which has one end engaged with the stop cock seat for sealing against the seat for prevention of flow of fluid from inlet to outlet, a piston located within the valve body and engageable with the valve seat, and biasing means operable to unseat the piston from the valve seat to enable the outlet to communicate with the valve body opening. In a further embodiment the valve assembly also includes a third seat in the handle and a valve member biased open by a spring against inlet pressure to allow atmosphere air to break a vacuum at the inlet. The fundamental advantage of the valve assembly is that it can prevent backflow when the stop cock is opened or closed and may also be utilized when the downstream pressure exceeds the upstream pressure by a predetermined amount.

TECHNICAL FIELD

This invention relates to a valve assembly for prevention of backflow intaps and faucets generally and which is attachable to the tap or faucet.

The invention will be described by way of example with reference to stopcocks but it should be appreciated that the invention is not limited tojust such an application. The valve of the invention may be used inother ways also. For example the valve of the invention may be used inrelation to globe valves which include inline stop cocks.

BACKGROUND ART

A normal stop cock valve tap consists of a body with an inlet, anoutlet, a valve seat between the inlet and outlet, a spindle with ahandle and a valve member movable by the handle to either cause it toseal against the seat or release it for movement away from the seat.

With such valves there is no protection against backflow and harmfulsubstances can travel into the supply line and contaminate liquid in thesupply line which may exit from that of other valves coupled to theline.

Backflow prevention devices are known and these are either fittedupstream or downstream of the valve. Where the valve is a standard stopcock, downstream backflow prevention devices may either be fitteddirectly to the outlet of the stop cock or in a line attached to theoutlet. Such devices can readily be removed and for this reason areundesirable.

Backflow prevention devices mounted upstream of the stop cock requirefitting by a skilled tradesman and are difficult to retrofit.

Reference may also be made to Australian specification 68314/90 whichdescribes a tap having the same construction as a conventional stop cockas described above which also includes a backflow preventer. In thisarrangement an operator is connected to a valve closure member whichopens and closes the flow passage between inlet and outlet. The backflowpreventer comprises a tubular body having a flow path therethrough whichis connected to the outlet and a non-return valve fitted within thetubular body. A vacuum break opening is formed in a wall of the tubularbody and there is also provided a diaphragm to open the opening andpermit communication between the atmosphere and the flow path when thepressure within the flow path is less than ambient pressure.

In Australian specification 69869/91 (EP441151) there is described amixer tap with a shower head attachment which incorporates a ventingdevice for preventing water from being drawn back via a hose connectionbetween a housing of the mixer tap and shower head. There is provided apair of valves inserted in a water feed for the shower head wherein eachvalve has a movable valve element displaced between two opposing valveseats respectively associated with a vent opening and a flow opening forthe water feed. Each valve element is biased towards the valve seatassociated with the water feed opening.

Australian specification 59050/90 describes a backflow preventer valveadopted to be fitted to a conventional tap or stopcock as describedabove. The valve has an inlet and outlet connected by one or morepassages and an annular main valve member formed of flexible materialwhich may move between a closed position when there is back flow throughthe valve and an open position when there is normal flow of liquid fromupstream to downstream. One or more discharge passages connect tointerior of the valve body to atmosphere on the downstream side of themain valve member. A spring loaded valve actuator closes the main valvemember when there is a back flow from the downstream side and alsocloses the discharge passage(s) when there is a normal flow fromupstream to downstream.

U.S. Pat. No. 4,969,483 describes an anti-siphon assembly especially fora shower mechanism which has an automatic flexible one way valveassociated with a cover of a housing of the anti-siphon assembly. Thecover has air intakes controlled by the one way valve. The valve has anelastic lip and remains closed while the pressure in a control valve ofthe shower mechanism is above atmospheric but opens as soon as thepressure drops below atmospheric in the control valve.

U.S. Pat. No. 4,909,270 describes an anti-siphon water backflow fittingwhich is fitted to a threaded neck portion of a faucet and which isadapted to receive a hose coupling. The fitting includes a pair ofvalves which are biased shut to prevent backflow of water into thefaucet when a water source is turned off and which are open when thewater source is turned on.

U.S. Pat. No. 4,804,010 describes a sink faucet assembly with ananti-siphon assembly forming a clamp for a sink deck.

U.S. Pat. No. 4,726,390 describes a faucet hose bib vacuum breaker orbackflow preventer which includes a web with multiple vent holes and aperipherally supporting flexible resilient diaphragm and overlyingplate.

U.S. Pat. No. 4,712,575 describes a self draining hose connection vacuumbreaker which has a movable piston with two different positionsdependent on whether or not the hose is fitted.

U.S. Pat. No. 4,712,574 describes a vacuum breaking valve for apressurised fluid line which has a pipe tapped into a line upstream ofan outlet terminating in a ball shaped housing. The housing receives acheck valve including a movable diaphragm arranged for ensuring thatfluid does not escape during normal operation of the line but admitsvacuum breaking air in the event of line pressure loss.

U.S. Pat. No. 4,700,732 refers to a faucet drain preventing damage dueto freezing having a lightly sprung ball valve allowing trapped water todrain when pressure is released.

U.S. Pat. No. 4,827,538 describes a mixing tap for a sink which has amixing chamber with a relief valve located in a wall of the mixingchamber which is responsive to negative pressure. The relief valvecomprises a closure member which is forced into a closed position bygravity and/or a spring.

U.S. Pat. Nos. 4,696,322 and 4,805,661 refers to a faucet back flowpreventer valve assembly which includes a control valve housing whichhas a valve member comprising a ball with ports for selectivelyuncovering or covering a supply inlet and outlet. A check valve ismounted in an anti-siphon passageway within the ball and allows air intothe ball from an auxiliary opening which communicates with atmosphereand hence into the supply inlet if negative pressure exists.

U.S. Pat. No. 4,669,497 refers to a water faucet backflow preventerassembly which includes a tubular body having a flow passageway havingan inlet and outlet. The flow passageway includes an integral shoulderand a pair of exhaust ports upstream of the shoulder. A valve assemblylocated within the passageway is spring biased into a seated positionclosing communication between the outlet and inlet while permittingfluid communication between the outlet and the discharge ports fordraining any reverse water flow. The valve assembly is yieldable to anoperating position under the force of pressurised fluid flow into theinlet and to open communication with the outlet. A resilient valvewasher contacts the integral shoulder to close communication between thepassageway and the discharge ports to prevent water leakage.

United Kingdom specification 1602193 refers to an anti-siphoning devicehaving a domed closure urged by atmospheric pressure to seal a matingaperture. The device is fitted into a garden water tap operated by ahandle, a spindle and an outlet and is mounted in the outlet.

U.S. Pat. No. 4,134,419 refers to a combination faucet and anti-siphonvalve having a body with two effluent inlets communicating with singleoutlet and central drinking water dispensing tube.

Having regard to the prior art described above which was located in aninternational search carried out in respect of the invention it will beappreciated that such prior art valve assemblies for preventinganti-syphoning or prevention of backflow were found to be deficient inoperation because of their inability to operate effectively wheninstalled in stop cocks or taps when the stop cock or tap was open orclosed.

DISCLOSURE OF THE INVENTION

It therefore is an objection of the invention to provide a valveassembly which in operation and when installed in a stop cock mayprevent backflow when the stop cock is open or closed.

The valve assembly of the invention is therefore attachable to a stopcock having an inlet, a seat, and an outlet, the valve assemblyincluding:

a valve body having at least one opening and also including a valvechamber and a valve seat; a balance tube in the valve body communicatingwith the valve chamber and having one end engageable with the stop cockseat in use for sealing against the seat for prevention of flow of fluidfrom inlet to outlet;

a piston within the valve body and engageable with the valve seat; and

biasing means operable to unseat the piston from the valve seat toenable the outlet to communicate with the valve body opening.

The piston preferably has a bore through which the balance tube maypass. Preferably the bore is centrally located relative to the pistonand extends longitudinally of the body. The bore may be sealed relativeto the balance tube. Preferably at least one piston seal is employed.More preferably, two spaced piston seals are employed.

The biasing means biasing the piston from the valve seat is preferably aspring. The spring may extend between the body and the piston.Preferably the spring extends between a shoulder in the body and thepiston. The spring may be a coil spring.

The chamber is preferably at one end of the body and spaced from thevalve seat.

The balance tube may be provided with an aperture for communicating withthe chamber. The aperture preferably is adjacent one end of the tube andlaterally of the tube.

The balance tube may be free to move against the seat in the stop cockunder the influence of gravity. The tube may be moved away from thatseat by fluid pressure at the inlet of the stop cock. Preferably biasingmeans is employed to bias the tube against the seat in the stop cock andinlet pressure may move the tube away from the seat against the actionof the biasing means.

The biasing means biasing the balance tube is preferably a spring, acoil spring is preferred. The spring may extend between the tube and thebody.

Preferably two openings are present in the body. The openings may bediametrically opposed.

The body may include a stop for limiting the movement of the piston. Thestop may project laterally of the body preferably the stop extendsthrough a wall of the body and consists of a fastener.

There also may be provided an air vent or inlet so that the valve bodymay be open to atmospheric pressure. The air inlet may be located in thestop cock handle if required or the stop cock body or valve body.

BRIEF DESCRIPTION OF THE DRAWINGS

A particular preferred valve assembly will now be described by way ofexample with reference to the drawings in which:

FIG. 1 is a sectional view of a valve assembly according to theinvention shown fitted to a stop cock and in the closed position;

FIG. 2 is a sectional view like that of FIG. 1 but with the valve in theopen position;

FIG. 3 is a sectional view of the valve assembly shown in a ventingposition preventing backflow;

FIG. 4 is a sectional view of a second embodiment of valve assemblyconstructed in accordance with the invention.

FIG. 5 is a sectional view of a third embodiment of valve assemblyconstructed in accordance with the invention, wherein the stop cock isin the closed position;

FIG. 6 is a similar view to FIG. 5 but showing the stop cock in the openposition;

FIG. 7 is a plan view of a sliding seal used in the embodiment of FIG.5; and

FIG. 8 is a plan view of a balance tube guide member used in theembodiment of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In FIG. 1 there is shown a stop cock 10 which may operate as a hose tapor faucet which may be used in gardens, laboratories, swimming pools,caravan parks, hairdressing salons or for use in sinks in kitchens. Thestop cock 10 includes an inlet 11 having a thread 11A attachable to aninlet pipe (not shown), a seat 12 and inlet 13 which are all standardfeatures of a conventional stop cock. A valve assembly 15 constructed inaccordance with the invention is screw fitted into the stop cock 10 at16. The stop cock 10 also includes handle 17 which has a spindle 17Ascrew threadedly engaged with bonnet 18 at 19. There is also provided anextension 18A of spindle 17A which is located in recess 19A of bonnet18. Extension 18A is provided with a seal 16A for movement within recess19A as spindle 17A is rotated from a closed position shown in FIG. 1 toan open position shown in FIG. 2. There is also provided a bush 10Awhich is screw threadedly attached to bonnet 18 at 14A and also screwthreadedly attached to valve body 20 of valve assembly 15 at 21.

The valve assembly 15 also includes seal 23 for providing a valve seat.Diametrically opposed openings 24 are also located in valve body 20.Opening 25 extends through the side wall of body 20 and communicateswith valve chamber 26. Opening 25 may be open to atmosphere or may beclosed off by a plug (not shown). Opening 25 may be used to test valveassembly 15.

Balance tube 30 is located within valve body 20 and has an internalpassage 31. There is also provided a guide member 22 for guidingmovement of balance tube 30. Guide member 22 is fixed to an upper end ofbalance tube 30 by screw threaded engagement. Lateral port 32 adjacentone end of balance tube 30 enables passage 31 to communicate with valvechamber 26. A lower end of the tube 30 terminates in a resilient member33 for seating against seat 12. Resilient member 33 is screw threadedlyengaged with tube 30 at 33A. A spring 34 is located between tube 30 andbody 20 and biases the tube 30 towards the seat 12.

Piston 40 has a bore 41 through which the tube 30 passes. Seals 42 and43, seal piston 40 against the tube 30 for relative sliding movement.Seal 44 seals the piston 40 against an internal surface 44A of valvebody 20. Spring 45 extends between the piston 40 and a shoulder 46 invalve body 20 and normally biases the piston away from seal 23.

The operation of the valve assembly 15 will now be described.

In FIG. 1 the spindle 17A has been operated to move the tube 30 againstseat 12. The valve assembly 15 is in the closed position. Fluid enteringthe inlet 11 does not exit from the outlet 13 but is free to communicatewith chamber 26 via passage 31 and aperture 32. Subject to any backpressure at the outlet 13 the piston 40 is held in the FIG. 1 positionagainst the action of spring 45 and abuts the seal 23. In this positionventing through openings 24 does not occur.

FIG. 2 shows the valve assembly 15 in its open position with the tube 30unseated from seat 12. Fluid may flow from the inlet 11 to the outlet13. Also this fluid communicates with chamber 26 to maintain the piston40 against seal 23.

In the event of loss of fluid pressure to the inlet 11, the pressure inthe chamber 26 decreases. Spring 45 forces the piston 40 away from seal23 to vent the valve body 20 to thereby break the syphoning effect fromthe outlet 13 to the inlet 11. This is shown in FIG. 3. When the inletpressure drops spring 34 ensures that the end of tube 30 engages theseat 12 shown in phantom in FIG. 3 thereby preventing further backflowfrom the outlet to the inlet of the stop cock 10.

The valve assembly 15 of the invention shown in FIGS. 1-3 functions suchthat the supply pressure controls the valve venting through the ventapertures 24 both when the valve is open and closed.

In FIG. 4 there is shown another valve assembly 10A in accordance withthe invention. In this arrangement there is also provided a flange 50and a balance pipe return spring 51. In the closed position shown inphantom in FIG. 4 water may enter the balance tube 30 and into valvechamber 26 through port 32. Water pressure may push the piston 40 downagainst the spring 45 so that the piston engages seal 23. Water pressurealso forces the flange 50 up against the balance pipe return spring 51.

In the open position shown in full outline in FIG. 4 when the stop cock10 is opened under mains pressure the balance tube 30 follows spindle17A up to the fully open position. When the stop cock 10 remains openunder pressure, the balance tube 30 and the seal 33 remain in the raisedposition regardless of downstream flow or no flow conditions. Theprovision of flange 50 therefore saves excessive wear and tear on seal33 and seat 12.

In FIG. 4 in the event of loss of supply pressure, water above thepiston drains through port 32 and the spring 45 forces the piston 40upwardly and opens the air vents 24. The return spring 51 forces theseal 33 to contact seat 12. In this position therefore no backflow canoccur and excess downstream pressure is released through air vents 24and air is allowed to enter and prevent back siphonage.

It will be appreciated that the embodiment of FIG. 4 is mainlyapplicable to an inline situation whereby inlet 11B shown in phantom maybe utilised instead of inlet 11. There is also shown outlet 13A whichmay be utilised in substitution of outlet 13 which is applicable to stopcock 10.

In FIGS. 5-6 a modified valve assembly 15B is shown in accordance withthe invention. In this arrangement there is shown an air inlet 60 inhandle 17 and spindle 17A. There is also included a floating seal 61which locates against seat 62. A spring 63 is located in air inlet 60and retained in position by shoulder 64. Floating or sliding seal 61 isprovided with a plurality of arms 65 allowing air to pass through gaps66 between adjacent arms 65.

The balance tube 30 is also provided with an upper fixed guide 67 whichalso has a plurality of arms 68 and gaps 69 located between adjacentarms 68. Guide 67 locates against shoulder 70.

Thus in operation of the arrangement shown in FIGS. 5-6 mains pressureforces sliding seal 61 against seat 62. The seal 61 is suitably madefrom plastics material of a relatively light weight. The balance tube 30is retained against shoulder 70.

The presence of negative pressure causes the sliding seal 61 to open airinlet 60 assisted by the bias of spring 63. Air may then enter chamber26 through gaps 66 in seal 61 and gaps 69 in guide 67 of balance tube 30and thence through port 32. This will enable the valve assembly 15B byopening of air vent or air inlet 60 to automatically prevent a vacuum orsource of negative pressure occurring upstream of valve assembly 15B.This is in contrast to valve assembly 15 shown in FIGS. 1-3 and valveassembly 10A shown in FIG. 4 wherein a vacuum or source of negativepressure will have already formed prior to elimination of the -vacuum aspreviously described in relation to valve assemblies 15 and 10A.

It will also be appreciated from the above in each of the threeembodiments described the valve assembly of the invention will operatewhether the stop cock 10 is in the closed or open position. Thus whenthe stop cock 10 is closed and balance tube 30 is in contact with seal12 the piston 40 will rise in the case of negative pressure upstream byvirtue of the bias of spring 45 so that the pressure can be relievedthrough air vents 24 as previously described. In other words the sourceof negative pressure upstream will cause a pressure drop which will beexperienced by valve chamber 26 being in communication with inlet 11 byvirtue of passage 31 and port 32. When the stop cock 10 is open thesource of negative pressure upstream in inlet 11 will also be relievedor prevented as previously described.

It will also be appreciated that the valve assembly of the invention canoperate effectively in the situation where downstream pressure willexceed upstream pressure by a predetermined or precalibrated amount. Inthis situation the balance tube 30 will remain in contact with seat 12and elevation of piston 40 will occur through the bias of spring 45.This occurs by virtue of the pressure on the underside of the piston 40(is the area defined by an annulus between sealing edges 46) which isnormally exceeded by the upstream pressure which is exerted on the topsurface 47 of piston 40 (which surface area is greater than the surfacearea of the abovementioned annulus) will then exceed the upstreampressure and thus cause elevation of piston 40. It therefore will beappreciated that the predetermined or precalibrated amount will bedirectly proportioned to the respective surface areas of the undersideannulus and top surface 47 of piston 40. This is a unique property ofvalve assemblies constructed in accordance with the invention which isnot realised by conventional backflow prevention valve assembliesreferred to above.

It therefore will be appreciated from the foregoing that the inventionis applicable to taps and faucets generally and in particular in regardto stop cocks which may be used to connect hoses thereto such as for usein swimming pools, laboratory sinks, public toilets, public buildings,factories, caravan parks and also in relation to irrigation where hosetaps or faucets or hose stop cocks are required.

The invention is also applicable to inline situations covering stopcocks or taps for use in dishwashers, washing machines, water softenersand other appropriate situations.

It will also be appreciated by the person skilled in the art that theadvantages of the valve assembly of the invention in contrast to theprior art will include the following:

1. Low cost

2. Can be retrofitted to all conventional taps or faucets.

3. Can be adapted to globe valves of all sizes.

4. Can be constructed in an alternate form such as a testable device andused in conjunction with a check valve as a low cost higher securitydevice.

5. Has low pressure loss characteristics.

6. Does not constantly leak to atmosphere during operation.

7. Downstream liquids may be released to atmosphere when upstreampressure is exceeded by downstream pressure ie. to a predetermineddegree of excess pressure.

8. May be essentially controlled by upstream pressure and allows theingress of air, upstream and downstream separately and in isolation fromeach other.

9. Is not easily removed as an inconvenience.

10. May operate when a stop cock is opened or closed.

I claim:
 1. A valve assembly suitable for backflow prevention in a stopcock having an inlet, a stop cock seat and an outlet and attachablethereto, the valve assembly including:a valve body having at least oneopening and also including a valve chamber and a valve seat; a balancetube in the valve body communicating with the valve chamber and havingone end engageable with the stop cock seat in use for sealing againstthe stop cock seat for prevention of flow of fluid from inlet to outlet,wherein the balance tube is free to move against the stop cock seatunder the influence of gravity; a piston within the valve body andengageable with the valve seat; and biasing means operable to unseat thepiston from the valve seat to enable the outlet to communicate with thevalve body opening.
 2. A valve assembly as claimed in claim 1 whereinthe piston is provided with a bore through which the balance tube maypass.
 3. A valve assembly as claimed in claim 2 wherein the bore issealed relative to the balance tube.
 4. A valve assembly as claimed inclaim 1 wherein there is provided biasing means biasing the balance tubeaway from the stop cock seat in use.
 5. A valve assembly as claimed inclaim 1 wherein the balance tube is provided with an aperture for fluidcommunication with the valve chamber.
 6. A valve assembly as claimed inclaim 5 wherein the aperture is located adjacent an end of the balancetube remote from said one end.
 7. A valve assembly as claimed in claim 1wherein the said at least one opening of the valve body is locatedadjacent a lower end of a side wall of the valve body in use.
 8. A valveassembly as claimed in claim 7 wherein there is provided a pair ofopenings in the valve body diametrically opposite to each other.
 9. Avalve assembly as claimed in claim 1 wherein said balance tube isprovided with a flange intermediate each end thereof and locatedupwardly of the piston in use.
 10. A valve assembly as claimed in claim9 wherein there is provided biasing means for biasing said flangedownwardly in use.
 11. A valve assembly as claimed in claim 1 whereinthe valve chamber is provided with an air vent above the piston which isopen to atmosphere.
 12. A valve assembly as claimed in claim 11 whereinthere is provided a sliding seal in the valve chamber for closing saidair vent during normal operation of the stop cock.
 13. A valve assemblyas claimed in claim 12 wherein the sliding seal has at least one airport for passage of air when the air vent is opened.
 14. A valveassembly as claimed in claim 12 wherein there is provided biasing meansfor biasing the sliding seal away from a mating seat to open the airvent.
 15. A valve assembly as claimed in claim 13 wherein the balancetube is provided with a guide member adjacent an upper end in use havingat least one air port for passage of air when the air vent is open. 16.A valve assembly suitable for backflow prevention in a stop cockcomprising an inlet, a stop cock seat, and an outlet and attachablethereto, the valve assembly including a valve body comprising:(i) atleast one opening in a side wall of the valve body and adjacent a lowerend thereof in use; (ii) a valve chamber; and (iii) a valve seat; abalance tube in the valve body provided with an aperture for fluidcommunication with the valve chamber, said balance tube being free tomove against the stop cock seat under the influence of gravity andhaving one end sealingly engageable with the stop cock seat in use forprevention of flow of liquid from inlet to outlet and there also beingprovided biasing means biasing the balance tube away from the stop cockseat in use; a piston within the valve body which is engageable with thevalve seat, said piston being provided with a bore through which thebalance tube may pass wherein the bore is sealed relative to the balancetube; and biasing means operable to unseat the piston from the valveseat to enable the outlet to communicate with the valve body opening.17. A valve assembly as claimed in claim 16 wherein the aperture islocated adjacent an end of the balance tube remote from said end.
 18. Avalve assembly as claimed in claim 16 wherein there is provided a pairof openings in the valve body diametrically opposite to each other. 19.A stop cock assembly comprising:a stop cock having an inlet, a stop cockseat and an outlet; a valve assembly attachable to the stop cock, saidvalve assembly including a valve body comprising:(i) at least oneopening in a side wall of the valve body and adjacent a lower endthereof; (ii) a valve chamber; and (iii) a valve seat; a balance tube inthe valve body provided with an aperture for fluid communication withthe valve chamber, said balance tube being free to move against the stopcock seat under the influence of gravity and having one end sealinglyengageable with the stop cock seat in use for prevention of flow ofliquid from inlet to outlet and there also being provided biasing meansbiasing the balance tube away from the stop cock seat in use; a pistonwithin the valve body which is engageable with the valve seat, andpiston being provided with a bore through which the balance tube maypass wherein the bore is sealed relative to the balance tube; andbiasing means operable to unseat the piston from the valve seat toenable the outlet to communicate with the valve body opening.
 20. A stopcock assembly as claimed in claim 19 wherein the stop cock is anexisting stop cock.